8/17/2013 12:40 AM PDT BY TMZ STAFF

EXCLUSIVE

NBA star Ryan Anderson is going through HELL right now following the suicideof GF Gia Allemand ... so says his ex-teammate Greivis Vasquez, telling our camera guy, Ryan needs his team more than ever right now.

The Sacramento Kings star knows Ryan from their days on the New Orleans Hornets (now Pelicans) -- and knew Gia very well from the 2 years she and Ryan dated. Of her death he says, "It's really tough. There are no words."

Vasquez says the toll it's taking on Ryan (who found her body) is painful to see. He explains, "It's just hard. I know he's feeling guilty." Adding, "We gotta support him. We gotta be there for him." He goes on.

As for how it might affect Ryan's NBA performance, Greivis remains optimistic.